Connect tail to fix position
If you want a fixed joint, you need a bone head in that position. Once you have setted the two joint bones, you can achieve the desired behaviour with constraints: IK, track to, stretch to, depending on the desired movements.

In my example a simple 2 bones IK chain targets toward the IK target bone, which will be extruded from the "fixed head" bone and setted as not deforming (uncheck its "deform" option).